THIS is How You Activate Your Core

When attempting to activate your core, the BRACE is far more effective than the HOLLOW. Bracing is the act of stiffening all three levels of the core simultaneously to create a 360 degree stabilization of the torso. Hollowing is an attempt to isolate a single muscle of the core (transverse abdominus), giving the exerciser a flexion response and very little overall stability. Think of a circus tent with a single pole in the middle (your spine). The guy wires that are attached to the pole at the corners and then to the ground give a buttressing effect that leaves the pole (your spine) stable. This is what happens when you brace. The muscles of the core work as a unit, giving equal amounts of support from all angles, resulting in superior stability.
Matt Pirtle MA CSCS